21.The armature torque of the D.C. shunt motor is proportional to

22.In case the back e.m.f. and the speed of a D.C. motor are doubled, the torque developed by the motor will

23.The speed of a motor falls from 1100 r.p.m. at no-load to 1050 r.p.m. at rated load. The speed regulation of the motor is

24.Buses, trains, trolleys, hoists, cranes require high starting torque and therefore make use of